Shell and tube type heat exchangers are widely used in a variety of industries in fluid heating or cooling applications. In its most common form, the shell and tube type heat exchanger consists of a plurality of parallel tubes arranged in a bundle, and fitting within a shell. One fluid is circulated through the tubes, while the second fluid circulates within the shell, over and around the tubes to effect thermal transfer between the fluids. Baffles are usually provided to direct the flow within the shell in several passes across the tubes to increase heat transfer, and in some cases fins are provided on the tubes to likewise increase heat transfer. Such fins are secured to the tubes in intimate contact therewith so that the fin essentially increase the surface area of the tube to increase heat transfer.
It is known to provide patterns or discontinuities on the fin surfaces to further improve the heat transfer rate. These patterns or discontinuities may consist of perforations, projections, indentations, and the like on either or both sides of the fin. Fin surface patterns are intended to increase flow turbulence, and as a result, the heat transfer rate.
However, there are certain disadvantages to adding fins and patterns or discontinuities thereon. For one thing, fins generally increase the pressure drop of the fluid flowing across the tubes within the shell, and this requires an increase in the power used to pump or circulate the fluid. Depending upon the application of the heat exchanger, and the heat and flow characteristics of the fluids involved, the increased heat transfer provided by the fins may be more than offset by increased power requirements for circulating the fluid. The same consideration holds for patterns or discontinuities in the fins to create flow turbulence, which will also increase pressure drop and power requirements. In addition, fin surface patterns or discontinuities if improperly designed can aggravate the problem of flow separation which ordinarily occurs on the downstream or back sides of the tubes and which results in a reduction in heat transfer.
Although many fin patterns for use on heat exchanger tubes are known in the prior art, they are still subject to some degree to the problems of excessive pressure drop, flow separations and inadequate heat transfer, depending upon the specific application of the heat exchanger.
The present invention provides an improved heat exchanger fin pattern that provides high efficiency in terms of high heat transfer rate and reasonably low pressure drop. The present invention's unique embossed fin pattern includes contours which guide the fluid flow around the tubes to significantly limit flow separation, and offers advantages over the prior art in that high density fluids requiring a high heat transfer rate can be handled by a heat exchanger using the fins embossed according to the present invention. This allows a heat exchanger to be constructed in a more compact arrangement, resulting in weight, space and costs savings.